How to send parameters using Laravel Mailable?

I want to send my user activation link through mail using Laravel Mailable. For sending mail .I did following way:

Mail::to($user['email'])->send(new RegisterEmail($user));

Where $user has the recently created user data.

And this is my RegisterEmail.php

class RegisterEmail extends Mailable
{
    use Queueable, SerializesModels;
    public $user;
    public function __construct($user)
    {
        $this->user = $user;
    }

    public function build()
    {

        return $this->from('abc@gmail.com', 'ABC co')
            ->subject('PlugNThemes Activation Code ')
            ->view('emails.activation')
            ->with(['name' => $this->user->name])
            ->with('link',$this->user->link);
    }
}

And here is the view part :

Welcome, 
Please active your account :  

But when the route called it's shows following Error on RegsiterEmail.php

Trying to get property of non-object

it couldn't get the $user data. How do i send user data to view page using build() method through RegisterEmail.php ?

via Chebli Mohamed